Multiple paternity increases effective size of southern Atlantic salmon populations

Abstract

Genetic analyses were performed on the progeny of Atlantic salmon (Salmo salar L.) sampled in natural redds of three rivers flowing into the Bay of Biscay, the Nivelle, the Mandeo and the Sella. These rivers are at the southern limit of the European distribution of the species and their populations are small and endangered by human activities. Nine variable number of tandem repeat (VNTR) loci (five minisatellites and four microsatellites) were used for parentage analysis. Multiple male participation was recognized in the fertilization of eggs. A large proportion was fertilized by precociously mature parr. We demonstrate that multiple paternity derived from mature parr is crucial for the conservation of genetic variability in small populations of Atlantic salmon.

Age Structure, Changing Demography and Effective Population Size in Atlantic Salmon (Salmo salar)

“…Mature male parr reproduction has been speculated to be beneficial for N e (Saunders and Schom 1985;L'Abée-Lund 1989;Martinez et al 2000;Valiente et al 2005;Juanes et al 2007), although mature parr may ''increase'' effective size only in the sense thatN e is increased compared to when mature parr are ignored in analyses (e.g., Jones and Hutchings 2002;Saura et al 2008). Nevertheless, the reasoning implies that parr reproductive contribution increases N e by reducing the variance in (male) individual reproductive success.…”

“…Nevertheless, the reasoning implies that parr reproductive contribution increases N e by reducing the variance in (male) individual reproductive success. Empirical investigations have often applied theory for discrete generations, through the influence of mature parr on sex bias (e.g., L'Abée-Lund 1989; Consuegra et al 2005) or individual reproductive success in a single breeding season (e.g., Martinez et al 2000;Taggart et al 2001). Both approaches may not correctly reflect processes in agestructured populations with overlapping generations.…”

“…We attempted to account for the influence of male parr maturation on age-specific reproductive contribution of males as follows. In the absence of data for the rivers, we used empirical values from observations under natural ( Jordan and Youngson 1992;Martinez et al 2000;Garant et al 2001;Taggart et al 2001) and experimental conditions (Hutchings and Myers 1988;Moran et al 1996;Thomaz et al 1997;Garcia-Vazquez et al 2001;Hutchings 2001, 2002). These studies suggest that mature male parr account for $30% of the fertilizations in direct competition with anadromous fish, over a wide range of operational sex ratios.…”

Interspecific barriers between salmonids when hybridisation is due to sneak mating

“…For identification of offspring of small sneaking males when a large salmon male is present (situation F), we have carried out paternity analysis employing VNTR loci (Martinez et al, 2000). Table 2 presents the results of the experiments carried out in the Lapitxuri channel.…”

“…Salmonids (Gross, 1985(Gross, , 1996, Blennioids (Neat, 2001), Poecilids (Pilastro and Bisazza, 1999) and other fish taxa exhibit very diverse male mating behaviour that vary from actively courting of the female to furtively release sperm when a female is courted by other males (sneaking). Small young Atlantic salmon males (called mature parr) which mature in the river before migrating to the sea exhibit a typical sneaking behaviour with a high fertilisation success in the wild (Martinez et al, 2000). At the southern edge of their geographical distribution, almost all Atlantic salmon males mature before seaward migration because freshwater maturation is enhanced by higher temperatures (Rowe and Thorpe, 1990;Prévost et al, 1992).…”